========================
Analysis of time average
========================

This page shows how to **calculate the time average** from the data with higher time resolution.

Resample function
-----------------

Resample is a convenient tool to convert data frequency and resample timeseries. 
For example, to resample a hour time series data, the command is the following:

Calculate hourly average
^^^^^^^^^^^^^^^^^^^^^^^^

For the calculation of the average for resampling periods, we can use ``.mean()``.

.. literalinclude:: programs/sample_timeave.py
   :language: python
   :lines: 1-6

The '1H' is the resample of data series for 1 hour, then calculate standard deviation.
The examples of time/date functionality are '1Y' (1 year), '2M' (2 months), '3D' (3 days), '4H' (4 hours), '5m' or '5T' (5 minutes), '6S' (6 seconds).

Standard deviation
^^^^^^^^^^^^^^^^^^

The resample function can be also used to get the maximum/minimum and calculate the standard deviation for a particular time period.

For the calculation of the standard deviation, we can use ``.std()``.

.. literalinclude:: programs/sample_timeave.py
   :language: python
   :lines: 1-4,8-9

If ddof = 0, the standard deviation is calculated from the number of data (N).
The default setting ``.std()`` is calculated from N-1.

The command ``.round()`` shows a variable number of decimal places. For ``.round(5)``, the data indicates 12.34567. 

Maximum/Minimum values
^^^^^^^^^^^^^^^^^^^^^^

.. literalinclude:: programs/sample_timeave.py
   :language: python
   :lines: 1-4,11-14

You can also write ``dat[var].resample('1H').max()``.

Plots
-----

Plots comparing two time range datasets.
The light-blue shaded lines are 5-minute data, and solid lines with markers are 6-hour average data. 
Both match, so you can confirm that the time average calculation is correct.

.. image:: SRC/TAIR.6hourly.png
   :width: 300

Sample porgram
--------------

The sample program calculates the time mean, maximum/minimum value, and standard deviation of the period (6 hours in this program) and plots the original data and the time average data.

Source file: :download:`cal_timeave.py <programs/cal_timeave.py>`